A substrate made of a brittle material (hereinafter referred to as substrate) having a size corresponding to a screen size is used for a flat panel display (hereinafter referred to as FPD).
In terms of panels for a liquid crystal display, which is a type of FPD, for example, two glass substrates are pasted together and liquid crystal is injected into the gap between these, and thus, a display panel is formed. In addition, in the case of a reflective type substrate inside a substrate for a projector, referred to as LCOS, a pair of substrates where a crystal substrate and a semiconductor wafer are pasted together is used. A pasted substrate where substrates are pasted together as described above is divided into unit substrates of a predetermined size, usually by drawing scribe lines on the surface of the pasted substrate, which is a mother substrate having a large size, and then breaking the substrate along the drawn scribe lines.
Here, drawing of scribe lines on a mother substrate is referred to as “scribing.” Folding and breaking of a mother substrate along a scribe line drawn through scribing is referred to as “breaking.” Dividing of a mother substrate into a brittle material substrate of a desired size through scribing and breaking is referred to as “dividing.” Furthermore, separation of a brittle material substrate that has been divided and conveyed after a dividing process into individual substrates is referred to as “separating.”
In addition, the properties of a scribing wheel for extending a vertical crack in the direction of the thickness of the substrate from the surface of the substrate by drawing a scribe line are referred to as “penetrability.”
FIG. 7 is a front diagram showing a publicly known scribing apparatus.
A conventional scribing method is described in reference to FIG. 7. Here, in this diagram, the left-right direction is the X direction and the direction perpendicular to the surface of the paper is the Y direction, in the following description.
A scribing apparatus 100 is provided with a table 28 on which a mounted glass substrate G is secured by means of a vacuum suction means and which is rotatable horizontally, a pair of guide rails 21, 21 which are parallel to each other and support the table 28 in such a manner that the table 28 can move in the Y direction, a ball screw 22 for moving the table 28 along the guide rails 21, 21, a guide bar 23 which crosses above the table 28 in the X direction, a scribe head 1 which is provided on the guide bar 23 in such a manner as to be slidable in the X direction and provides pressure for cutting to a scribing wheel 50, a motor 24 for sliding the scribe head 1 along the guide bar 23, a chip holder 11 which is provided at the lower end of the scribe head 1 in such a manner as to be able to freely oscillate and is raised and lowered by the scribe head 1, a scribing wheel 50 which is mounted at the lower end of the chip holder 11 in such a manner as to be rotatable, and a pair of CCD cameras 25 which are installed above the guide bar 23 and recognize alignment marks formed on the glass substrate G on the Table 28.
FIGS. 8 and 9 are diagrams illustrating the process for dividing a brittle material substrate, for example a glass substrate, that is to say, the respective steps of drawing a scribe line on the surface of a brittle material substrate and breaking the brittle material substrate along the drawn scribe line so that the substrate is divided into brittle material substrates of a desired size.
In reference to FIGS. 8 and 9, two examples of the process for dividing a substrate are described. Here, in the following description, a glass substrate G, which is pasted glass used for a panel for a liquid crystal display, is used as an example, and for the sake of convenience, the glass substrate on one side is referred to as substrate on side A and the glass substrate on the other side is referred to as substrate on side B for the time being.
In the first example, (1) first, as shown in FIG. 8(a), a glass substrate G is mounted on the scribe table of the scribing apparatus with the substrate on side A facing upward, and the substrate on side A is scribed using the scribing wheel 50 so that a scribe line Sa is drawn.
(2) Next, the glass substrate G is turned upside down and the above described glass substrate G is conveyed to a breaking apparatus. Then, as shown in FIG. 8(b), a breaking bar 3 is pressed against the substrate on side B of the glass substrate G mounted on a mat 4 along the line facing the scribe line Sa in this breaking apparatus. As a result, a crack extends upward from the scribe line Sa in the lower side substrate on side A, and thus, the substrate on side A is divided along the scribe line Sa.
(3) Next, the glass substrate G is conveyed onto the scribing table of the scribing apparatus. Then, in this scribing apparatus, as shown in FIG. 8(c), the substrate on side B is scribed using the scribing wheel 50 so that a scribe line Sb is drawn.
(4) Next, the glass substrate G is turned upside down and conveyed to the breaking apparatus. Then, as shown in FIG. 8(d), the breaking bar 3 is pressed against the substrate on side A of the above described glass substrate G mounted on the mat 4 along the line facing the scribe line Sb. As a result, the crack extends upward from the scribe line Sb on the lower side substrate on side B, and the substrate on side B is divided along the scribe line Sb.
In the present invention, the dividing method made up of the above steps is referred to as SBSB method (S means scribing, and B means breaking).
In addition, in the second example, (1) first, as shown in FIG. 9(a), a glass substrate G is mounted on the scribe table of the scribing apparatus with the substrate on side A facing upward, and the substrate on side A is scribed using the scribing wheel 50 so that a scribe line Sa is drawn.
(2) Next, the glass substrate G is turned upside down, the above described glass substrate G is mounted on the scribing table, and the glass substrate on side B is scribed using the scribing wheel 50 so that a scribe line Sb is drawn (FIG. 9(b)).
(3) Next, the glass substrate G is conveyed to a breaking apparatus. Then, as shown in FIG. 9(c), the breaking bar 3 is pressed against the glass substrate on side B of the glass substrate G mounted on the mat 4 along the line facing the scribe line Sa in this breaking apparatus. As a result, the crack extends upward from the scribe line Sa on the lower side substrate on side A, and the substrate on side A is divided along the scribe line Sa.
(4) Next, the glass substrate G is turned upside down and, as shown in FIG. 9(d), mounted on the mat 4 in the breaking apparatus. Then, the breaking bar 3 is pressed against the substrate on side A of the glass substrate G along the line facing the scribe line Sb. As a result, the crack extends upward from the scribe line Sb on the lower side substrate on side B, and the substrate on side B is divided along the scribe line Sb.
In the present invention, the dividing method made up of the above described steps is referred to as SSBB method.
By carrying out the respective steps (1) to (4) in the two above described examples, a glass substrate G is divided in two along a scribe line in a desired location. Furthermore, the glass substrate G is separated at desired locations for separation through application of light force.
In addition, Patent Document 1 discloses a scribing wheel having high penetrability.
Patent Document 1: Japanese Patent No. 3,074,143
FIGS. 11 and 12 are schematic diagrams (including a diagram showing an enlargement of a certain portion) for illustrating the scribing wheel of Patent Document 1.
A scribing wheel 40 is formed of an outer peripheral portion around which a circumference ridgeline 41 is formed, and a great number of alternating notches 40b and protrusions 40a formed along the circumference ridgeline 41 in the direction of the circumference. The protrusions 40a are formed by notching the circumference ridgeline 41 with a predetermined pitch and depth. A vertical crack which is deep relative to the thickness of the glass substrate can be formed in the glass substrate from the surface in the vertical direction by drawing a scribe line using the scribing wheel 40. In the case where such a scribing wheel 40 having high penetrability is used in the dividing process, it becomes possible to simplify or omit the breaking process in accordance with the SBSB method shown in FIGS. 8(b) and 8(d), or the breaking process in accordance with the SSBB method shown in FIGS. 9(c) and 9(d).
Furthermore, as a result of improvements in the material for substrates by makers of glass materials and various types of improvements in heat treatment, a state of “poor catch” may ensue, that is to say, there may be cases where scribe lines do not start being drawn immediately after the rotation of the wheel at the time of scribing using a conventional cutter wheel (conventional blade (normal blade); hereinafter referred to as N blade). That is to say, it has been observed that the blade tends to “easily slip” on the surface of the substrate. As a result of this, blades with “good catch” have started being required. However, it is possible for the blade with high penetrability (hereinafter referred to as P blade) described in Patent Document 1 to provide “good catch” but it has become difficult to secure the quality standard in terms of the strength of the end surface required at the manufacturing site for FPD panels. Though in terms of the strength the end surface, data on surfaces divided using an N blade is favorable, there are the following problems described in reference to FIG. 10 in the case of N blades.
FIG. 10 is a schematic diagram showing a case of cross scribing on a single substrate. There are problems in the case where such a cross scribing method using an N blade is employed, such that scribe lines do not continue in the vicinity of intersections and so-called “intersection skipping” may occur.
Though in terms of the above described strength of the end surface, data on surfaces divided using an N blade is favorable, there are problems, such that (1) intersection skipping occurs in cross scribing, (2) good catch is required for substrates having a high level of hardness on the surface, and (3) though a scribing method using inner cutting is required for glass having a thickness of 0.4 mm or less and glass of which the thickness has been reduced through chemical treatment, for example chemical etching, N blades cannot cope with this.
Meanwhile, in the case where it is desired for a scribing method using a P blade to be adopted, some sites of mass production for FPD panels require tasks that can be dealt with in conventional breaking processes, in which case introduction of a P blade does not necessarily become a solution. In addition, in terms of the strength of the end surface, use of a P blade is in some cases restricted.
Though the number of cases where a mother substrate which is a material for a panel substrate is chemically etched in order to reinforce the strength on the surface of the substrate in addition to improvement of the surface strength of substrates has been increasing, in such cases, the outer periphery of the substrate bulges and the scribing operation through “outer cutting” (outer cutting scribing operation) tends to become unstable. In addition, there has been a rising tendency of panel substrates used for portable terminals, such as cellular phones, becoming thinner and thinner with reduction in weight as a purpose, and problems arise with such substrates when an outer cutting scribing method using an N blade is adopted. The reason for this is that when an outer cutting scribing method is adopted for a thin substrate, impacts at the edge of the end surface of the substrate may cause chipping at the edge or cracking of the substrate itself when the cutter wheel rolls onto the substrate, and thus, the yield of products lowers. Accordingly, outer cutting scribing using an N blade cannot be adopted for thin substrates. However, N blades are blades with poor catch, and therefore, an inner cutting scribing method using such a blade cannot be adopted.
For the reasons described above, the user of the blade has required a blade having good catch on the surface of substrates, that is to say, a blade which makes it difficult for intersection skipping to occur and can secure quality for the end surface, so that the strength is approximately the same as that of N blades.